Well I spent most of 2009 developing a heliostat prototype, and over the last year I've realized that I'm not in the position to go entrepreneurial with it so I'm just putting it out there....

heliostat.sourceforge.net is the home page. It's spankin' new and I'll flesh it out a little better soon.

I started the project with the 328 and filled that up, then split tasks between two 328s communicating over I2C, then found out the solar code wouldn't fit at the same time that the Mega128 support came out, so that was cool. I use a simple TIP 12X H-bridge to drive two satellite dish linear actuators. They have a reed sensor that gives a pulse which is hooked up to an Arduino interrupt for position sensing. An old bicycle frame turned upside down and slightly modified made a great Alt-Azimuth mount. I used a basic LCD keypad shield for user I/O to keep things cheap. The prototype stand with a 4'x4' mirror assembly mounted has even survived a thunderstorm with 40mph gusts and 3/4" hail without any damage to the mirrors.

I've developed this entire project while largely unemployed and semi-homeless, which has at times given it a rather surreal feeling. Whatever was at hand that could be used got used, and purchases were kept to a minimum. Without wasted dead end R&D expenses, the basic prototype that I built could be duplicated for about $350.

The perhaps more complicated part has been building a suitable target device. I've almost finished a bio-mass fueled water heater design that only needs a slightly different heating element for solar use. I've learned that boilers can be dangerous if you don't have the right regulators! If I can just get the wiring right on the DS18b20 sensors then I'll be able to finish my Temperature Differential Controller project.

The vision is to have a small residential "farm" of heliostats that act as slave devices to smart targets which act as master devices in a dynamically distributed solar energy network, with various priority levels for targets resolving allocation conflicts at the heliostat level. All this going over an XBee network would be cool.

Comments, suggestions, support, and encouragement are all appreciated.

Hey emdee, awesome work! I'm working on a slightly similar project that involves tracking the sun for an active skylight (http://arduinobeam.blogspot.com/). Why is it your sun position calc wouldnt fit on a 328? I'v had a look at the NREL code you mention on your site and seems like a really reliable source. Would be real keen to see your stripped down version and possibly improve the accuracy of my setup.

I think this is great. You could use it to boost the lighting in a home by specifying windows as targets (I live in a country where you have to have the lights on during the day for a big chunk of the year).

You could even have it follow you round the house if you have the network setup with PIR sensors.

Nice project and nice web page you have set up there. I especially like the reusing of common materials (bike frames) as it fits so well with the spirit and budget of most hobbyist.

Two points:

You mention here and on your site you are using the Mega128 chip, however I think you mean the Mega1280 chip as used on the orginal Arduino mega board. There is a Mega128 chip and is used in a board by the open source wiring project, however the Mega128 chip is not directly supported by the Arduino IDE without modification to some of the files.

Nice that you found out one of the universal laws of pratical electronics: The semiconductor(s) will always fail first to protect any fuse used in the system.